Yes I agree that intentional interference will most likely happen when crowns are on the line etc, but unintentional interference will happen in all tiers, and I don't see why you'd need this extra time, the offer lasts for an hour and if they take it you can both wave right off the bat, neither side is really unfairly advantaged from the current system.
And I don't think we should add additional protected time so I'm against adding any "warlike protection" to your 12 hours.